Simple timber buildings are ripe for retrofits This cute Nova Scotia EnerPHit project points to the potential in NZ

18 March 2024 by Jason Quinn

This Canadian retrofit project is encouraging: it’s an old timber-framed and clad building with single-paned glazing in timber frames. Built in the 1850s, it’s older than the New Zealand homes built from the same materials. Regardless, it’s this kind of construction that offers the best retrofit potential in New Zealand—even better if they are two-storey like this Nova Scotian example. The building will become the office of a local architectural firm. 

The main challenge with retrofits is economic: how can you get a good outcome for less money than you’d spend on demolition and starting over? The general rule of thumb is keep either the outside or the inside of the building. But you have to run the numbers because sometimes an interior and exterior retrofit can made sense. One of the key things to look for is the simplicity of the building form. A simple rectangular or square form really helps with the economics of retrofitting. Fewer corners, lower costs! (Two-storey state-built duplexes are ripe for deep energy retrofits, as Passive House designer and architect Murray Robertson discovered—see his blog posts, starting here). 

Two main reasons drive this. Firstly, the work on-site is drastically simpler with a simple form. Second, a simple form delivers a better form factor. When it comes to form factors, the lower the number the better. Simple two-storey buildings like this example can easily have a form factor below 2.5. That will lower insulation requirements significantly while still meeting the EnerPHit standard.

The article on this project is really worth a read. Please note that this project is using the component method for their EnerPHit certification. This is one of two routes to EnerPHit certification and can simplify the process. It will help this project as the existing glazing is not ideally orientated. Fire walls and property boundaries significantly constrain alterations. This project is targeting an 88% reduction in GHG emissions and an 87% cut in energy use. Energy modelling at design stage predicted heating energy savings of 92%.

We’ve published case studies of two significant EnerPHit projects in New Zealand, which you can read about here: Till Cottage and Piha EnerPHit. Plus there’s some more background and behind-the-scenes images on the ground-breaking Piha project here.


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